Portable data carriers with microprocessor control are well known. One such device is disclosed in U.S. Pat. No. 4,211,914, to Drexler, issued Aug. 8, 1980. This patent discloses a secure data storage system using both magnetic and optically encoded data on a card. The data storage system of the '914 patent illustrates the use of a microprocessor and read-only memory (ROM) to evaluate the character of the data after a data transaction. The data storage system of the '914 patent is particularly directed to error recognition in data which is to be stored, unlike the present invention, which utilizes an optically scanned memory to increase the data capacity of discrete memory devices of a computer system and to decrease the response time of the system. The memory capacity and response time of a computer system are improved in the present invention by juxtaposing a semiconductor or other discrete memory device and a rotating optical medium with multiple read-write heads, operating in a virtual-page mode to replace or extend the discrete memory.
In addition, data cards for retention or revision of data in a remote-data acquisition system are also known. One such data card is disclosed in U.S. Pat. No. 3,978,320 to McBride Jr., in which a card readable by a magnetic card reader is used to display and update inventory data. Unlike the present invention, which uses an optical laser scanner, the '320 patent teaches an electromagnetic data accessing system that includes a magnetic card reader and card-holding matrix to access data. The data card of the '320 patent does not use a data storage function to replace or extend the capacity of discrete memory devices of a computer system as does the present invention. In addition, the apparatus of the '320 patent does not decrease the response time of the computer system, as does the present invention.
Several known systems for laser optical encoding on plates or strips of optical media have been presented in the general field of memory-recording media. The read-write laser optical card system and related technology utilized in the present invention is well known in the art, as exemplified by U.S. Pat. No. 4,360,728, to Drexler, entitled "Banking Card for Automatic Teller Machines and the Like," and U.S. Pat. No. 4,314,260, also to Drexler, entitled "Laser Pyrographic Reflective Recording Layer in a Carbon Containing Absorptive Matrix." The '728 patent discloses a data card with a pair of spaced information records. One record is a strip of high-resolution reflective laser recording material. The other information record is of a magnetic recording material. An external card reader is needed to examine data on the information records or strips and to make additions to the "read-after-write" laser strip contained on the card. The reflective laser recording material is perforated by the laser in order to encode data on the card and to allow the read head assembly to read the data from the card. This external card must be introduced into a remote card reader-writer to verify, modify or reject data already on the card. This invention is particularly applicable to user-card identification applications.
The Drexler '260 patent discloses a laser pyrographic reflective recording layer using a rotating disk for fast random access to the information stored on the layer. The '260 patent also discloses the use of stacked plates for intermediate-speed random access by means of an electro-optical scanner.
The present invention uses the advantages of the laser pyrographic reflective recording layer as disclosed in the Drexler '260 patent to provide a very high-density data medium coupled with a remote data-card storage system. The optically encoded memory system is an extension of the random-access memory (RAM) of a computer system in its ability to write and read computer information rapidly to and from the data card. Further, the memory system of the present invention extends the capacity of the discrete RAM of the computer without changing its characteristics as viewed by a user. An optical laser scanner coupled with virtual memory techniques and hardware, as used in the present invention, provides rapid data searching, resembling the operation of true read-write semiconductor RAMs.
Semiconductor RAMs have not previously been compatible with some multiple-processor architectures, particularly hand-held portable architectures, because of limitations on the available physical space. Previously, serial configurations in memory systems caused relatively long wait states while writing to or reading from the read-write optical laser memory. This occurred when the required computer information was not available in the bit slice processor of the cache memory at the required time because the desired computer information was at the extremities of the optical strip, or in other words the farthest geographic location from the nominal position of the optical reader.
The present invention increases the read-write speed of a computer system by including virtual memory operation and having a bit slice processor which is in communication with a main processor by means of a processor bus and an input-output bus. Such a configuration significantly accelerates the retrieval time of the system, making computer information available for use by the main processor in a timely fashion. Use of an optical laser scanned medium with virtual memory operation is a significant improvement in the area of available "on-board" active memory space, providing reduced physical size of the system while decreasing the accessing time of such a system. Moreover, the use of a multiple- processor architecture, in combination with this type of memory medium, brings large-scale performance to moderate size geometries and price structures in a way that was previously unavailable in the computer market.